Grass mowing machines known as zero turning radius (“ZTR”) mowers have at least one independently powered drive wheel on each side of a frame. One drive wheel may be operated in a forward direction while the other drive wheel may be stopped or operated in reverse. Many ZTR mowers have a twin stick control system. A pair of control levers or sticks may be provided side-by-side, with each lever or stick controlling one of the drive wheels. When both levers or sticks are advanced together forwardly out of their neutral position, both drive wheels rotate forwardly to cause the mower to move forward. A ZTR mower may be steered by advancing one lever or stick more than the other.
Typically, each control lever or stick on a ZTR mower may be linked to a pump arm of one of two separate hydraulic pumps, or of a dual hydraulic pump; i.e., a separate pump for each wheel. The lever or stick may be used to move a pump swash plate through a direct linkage.
The control levers or sticks on a ZTR mower may be mounted on the vehicle frame so that each has a first pivot axis allowing the lever or stick in the operating position to pivot forwardly in an arc to turn the wheel in forward, or pivot rearwardly to turn the wheel in reverse. Additionally, the operator can pivot each lever or stick to a neutral operating position, and then pivot each lever or stick outwardly in an arc to a non-operating or park position. If both levers or sticks are pivoted to neutral, the ZTR mower should be stationary, both levers or sticks should be at the same position, and both levers or sticks should align with slots so that they can pivot outwardly to park. An operator may need to make neutral adjustments to the linkages if the levers or sticks are misaligned in the neutral position, due to wear, age or loosening of components of the ZTR mower.
Neutral adjustments for levers or sticks on ZTR mowers typically require the operator to step off the machine to make the adjustments. The operator may have to flip up the seat or remove a panel to access the adjustment points. Once the operator can access the steering linkages, he or she must loosen the links, which may be include turnbuckle and/or jam nuts, to make the adjustments. The operator then must retighten the steering linkages. The operator also may need to lift the rear of the unit off the ground to prevent the machine from moving during the adjustment.
There is a need for a simple and inexpensive neutral adjustment mechanism for dual lever steering controls on a ZTR mower that does not require the operator to get off the machine while making the adjustments. A neutral adjustment mechanism is needed that does not require flipping up a seat, removing a panel, lifting the rear of the machine, or turning off the machine to access the adjustment points. A neutral adjustment mechanism is needed that allows adjustments to be performed with minimal effort.